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Long-QT Syndrome in Boys


ROCHESTER, N.Y. -- Boys ages 10 to 12 with long-QT-syndrome are four times more likely to have aborted cardiac arrest or sudden cardiac death than age-matched girls with the syndrome.

ROCHESTER, N.Y., Sept 14 -- Boys ages 10 to 12 with long-QT-syndrome are four times more likely to have aborted cardiac arrest or sudden cardiac death than age-matched girls with the syndrome.

So found an analysis of data from the International Long QT Syndrome Registry, reported in the Sept. 13 issue of the Journal of the American Medical Association by Jenny B Hobbs, M.D., of the University of Rochester, and colleagues.

Other predictors of aborted cardiac arrest and sudden cardiac death for these young patients were timing and frequency of syncope and degree of QTc prolongation, they found.

Although syncope was the strongest predictor-with increased risks as high as 18-fold greater for those with two or more recent fainting events-these patients reduced their risk of aborted cardiac arrest and sudden death by 64% with beta- blockers.

Beta-blocker therapy did not, however, reduce events in low-risk patients nor did they reduce events when the data were analyzed in a sudden-cardiac death only model. But the benefit was so pronounced among the high-risk group that the authors concluded that use of beta-blockers for all patients with long-QT-syndrome "remains prudent."

The study involved 2,772 registry participants who were alive at age 10 and were followed until age 20. Registry enrollment began in 1979 at five participating centers in the United States and Europe and follow-up of aborted cardiac arrest and sudden cardiac death ended on Feb. 15, 2005.

Eighty-one participants had aborted cardiac arrest. Nine of these had subsequent cardiac death and 45 had sudden cardiac death.

Among the findings:

  • Those who had one syncopal episode in the previous two years were almost 12 times more likely to have a life-threatening event (hazard ratio 11.7; 95% confidence interval 7.0 -19.5; P<0.001). For those who had at least two recent syncopal episodes the risk was higher still (HR 18.1, 95% CI 10.4-31.2; P<0.001).
  • Compared with those who had no syncopal events during the previous 10 years, patients with one syncopal event in the previous two to 10 years-but no fainting in the previous two years--had almost a threefold increase in risk for life-threatening events (HR 2.7; 95% CI 1.3-5.7; P<0.01).
  • Compared with those who had no syncopal events in the previous 10 years, those who had two or more fainting spells over the previous two to 10 years but no recent syncope had almost a sixfold increase in risk (HR 5.8; 95% CI 3.6-9.4, P<0.001).
  • A QTc threshold of 530 milliseconds or more was associated with a hazard ratio of 2.3 (95% CI 1.6-3.3; P<0.001) compared with those with a shorter QTc.
  • Compared with same-age girls, boys 10 to 12 had a hazard ratio of 4.0 for life threatening events (95% CI 0.2-0.7; P<0.01). There was no significant risk difference between males and females between the ages of 12 and 20.

The three factors for estimating risk-timing and frequency of recent syncope, the duration of the QTc interval and gender-can be used to as a "useful guide for prophylactic treatment decisions to reduce the risk of sudden death in patents with [long-QT-syndrome] during the high-risk teenage years."

In contrast to previous studies, the investigators detected no significant association between genotype and life-threatening events.

The study was funded in part by NIH grants and a research grant from Genissance Pharmaceuticals (now Clinical Data). One of the authors is a consultant for Clinical Data and holds significant interest in intellectual property related ion-channel mutants. Another author reported that she has a patent pending for a screening algorithm for genetic testing in long-QT syndrome.

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